1. Field of the Invention
The present invention relates to an image forming apparatus provided with a registration roller.
2. Description of the Related Art
In general, an image forming apparatus, in order to transfer a toner image formed on a photoreceptor to a sheet with accuracy, stops the sheet once at a nip portion of a registration roller pair immediately before the photoreceptor, and adjusts a position of a leading end of the sheet and feeding timing. Then, the registration rollers are rotated based on transfer timing of the toner image, and the sheet nipped between the registration roller pair is fed out to a transfer position.
As described above, in order to position the leading end of the sheet, the leading end of the sheet being fed from an upstream part of a feeding path is brought into contact with the registration roller pair, and the sheet is stopped. In the image forming apparatus having the registration roller, a mechanism for allowing the registration roller to slide in a sheet width direction and a means for detecting a position of a side end part of the sheet in parallel with a feeding direction of the sheet are provided, and the side end parts of the sheet are positioned in a main scanning direction (sheet width direction).
Patent Literature 1, for example, describes a paper feeding device having a resist photosensor for detecting a leading end of a sheet (transfer paper), which is mounted integrally with the pair of registration rollers.
FIG. 9 is a flowchart illustrating an outline of paper feeding processing by the paper feeding device described in Patent Literature 1.
In the paper feeding device described in Patent Literature 1, when a sheet is supplied from a paper feeding stage and paper passing is started (Step S101), the resist photosensor performs detection of a leading end of the sheet being fed (Step S102). When the resist photosensor detects the leading end of the sheet, the paper feeding device brings the leading end of the sheet into contact with the pair of registration rollers and stops the sheet and then, causes the leading end of the sheet to enter the nip portion formed at the registration rollers (S103). Here, when a side-end detection sensor in the paper feeding device detects deviation of the sheet from a reference position in the sheet width direction (Step S104), the paper feeding device swings the registration rollers until the deviation is not detected any longer (Step S105). After the swing of the registration rollers is finished, the paper feeding device feeds the sheet to the transfer position (Step S106). At the transfer position, a toner image is transferred to the sheet (Step S107).    Patent Literature 1: Japanese Patent Laid-Open No. 06-40608